A rotary magnetic head assembly 1 used in, for example, an 8 mm video tape recorder consists of a pair of rotary heads H.sub.A and H.sub.B having different azimuth angles which are provided so as to keep an angular spacing of nearly 180.degree. therebetween and a rotary drum 2 around which a magnetic tape 3 is obliquely wrapped over an angular range of a little over 216.degree. as shown in FIG. 1.
FIG. 2 shows a track pattern formed by the rotary heads H.sub.A and H.sub.B when they trace the magnetic tape with the above tape wrapping angle, in which each of the slant tracks 4A and 4B is divided into a video signal recording interval (hereinafter a video interval) T.sub.V and an audio signal recording interval (hereinafter an audio interval) T.sub.A shown by a hatched area.
The audio interval T.sub.A is assigned to a duration of a rotation angle of nearly 36.degree. of the rotary heads H.sub.A and H.sub.B when they have begun to contact with the magnetic tape 3, while the video interval T.sub.V is assigned to the remaining duration of nearly remaining 180.degree.. A video signal of one field amount is recorded in the video interval T.sub.V. In the audio interval T.sub.A, there is recorded an audio signal relating to the video signal of one field amount as a PCM digital audio signal under the condition that the time base thereof is compressed.
There is proposed such an 8 mm video tape recorder having such tape format which can be used also as an audio tape recorder U.S. Pat. No. 4,542,419 issued Sept. 17, 1985.
According to the technique disclosed in the above patent, when the video tape recorder is used only as an audio tape recorder, the video interval T.sub.V is used as the audio interval T.sub.A. Since the video interval T.sub.V is 5 times as long as the audio interval T.sub.A, the audio intervals T.sub.A of .circle.0 to .circle.5 can be recorded each of the slant tracks 4A and 4B as shown in FIG. 3. Accordingly, when the audio signal from the same source is recorded, the recording time becomes 6 times as compared with that when being used as the video tape recorder. Further, when different audio signals are recorded on the respective audio intervals T.sub.A of .circle.0 to .circle.5 , the audio signals of 6 channel amounts can be recorded simultaneously.
By the way, since the audio signal is the PCM digital audio signal as described hereinabove and the sampling frequency thereof is 2f.sub.H (f.sub.H is the horizontal frequency), the frequency band thereof is narrower than that of the audio signal reproduced from a PCM audio compact disc and hence the quality of the audio signal is deteriorated.
That is, according to the audio tape recorder provided by the prior art disclosed in the above published document, the recording time can be prolonged or the number of the recording channels can be increased but the tone quality is not improved at all.
Therefore, this invention is to propose an information signal recording apparatus which can improve a tone quality of an audio signal obtained when the apparatus is used as only an audio tape recorder and which is arranged to be compatible so that an audio signal, which is recorded to improve the tone quality, can be reproduced by a prior art audio tape recorder.